Project at a Glance

Title: Heterogeneous NOx chemistry in polluted urban atmospheres: implications for the formation of particles and ozone and control strategy development.

Principal Investigator / Author(s): Barbara J. Finlayson-Pitts

Contractor: UC Irvine

Contract Number: 00-323

Research Program Area: Atmospheric Processes

Topic Areas: Chemistry & Reactivity


Experimental laboratory studies of heterogeneous reactions of oxides of nitrogen were carried out using a variety of spectroscopic techniques. This included the development and application of a new chamber that combines long path infrared analysis for gases with attenuated total reflectance infrared analysis for simultaneous measurement of the chemistry occurring in the thin surface film. The reactions studied included the heterogeneous hydrolysis of NO2 to form gas phase HONO and surface-adsorbed HNO3, “renoxification” reactions of adsorbed nitric acid with NO to regenerate NO2 and the effects of light on the production of gas phase HONO. The nature of the thin water film on the surface that provides the milieu for this chemistry was also explored and the changes in the film characterized as a function of relative humidity. Finally, the interactions of gas phase HONO itself with surfaces were explored and it was shown that a competition between HONO and water for surface sites is a major determinant of how much HONO is released to the gas phase. Preliminary airshed modeling of the renoxification process suggests that such chemistry may be significant in determining ozone and particle concentrations in polluted urban atmospheres and highlights the importance of including heterogeneous reactions in the boundary layer in current airshed models.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

Stay involved, sign up with CARB's Research Email Distribution List